NEW DELHI 
Pakistan is shifting blame and responsibility for last month's deadly attacks in Mumbai, India's foreign minister charged Monday, adding that Delhi would take action against the perpetrators if Islamabad failed to.

India also gave Pakistan a letter written by Mohammed Ajmal Kasab, the only gunman captured after the rampage. Kasab wrote that he and the nine other gunmen involved in the Nov. 26 attack all came from Pakistan, India's Foreign Ministry said. He also requested a meeting with Pakistani envoys, the ministry said.

Islamabad has not acknowledged that Kasab is Pakistani and has said it is waiting for proof of his citizenship before it will take further action.

India's Foreign Minister Pranab Mukherjee said that if Pakistan doesn't deal with those responsible, India was prepared to "take all measures necessary as we deem fit to deal with the situation." He did not elaborate about the measures.

"Unfortunately, Pakistan's response so far has demonstrated their earlier tendency to resort to a policy of denial and to seek to deflect and shift the blame and responsibility," he told a meeting of Indian envoys in Delhi.

The investigation into the attacks that killed 164 people has heightened tensions between India and Pakistan, longtime rivals that have fought three wars since gaining independence from Britain in 1947.

On Monday, fighter jets flew low near several of Pakistan's major cities in exercises that briefly delayed two Pakistan International Airlines flights, airline officials said.

Pakistan's air force declined to comment on the flights but issued a statement saying that "in view of the current environment, the Pakistan Air Force has enhanced its vigilance."

Now that it has Kasab's letter in hand, Pakistan faces pressure to answer to India's demands that it turn over wanted leaders of the Pakistan-based militant group, Lashkar-e-Taiba, accused of plotting the attacks.

"We are examining the letter," Pakistan High Commission spokesman Abid Saeed said late Monday.

Pakistan has moved against both Lashkar-e-Taiba and Jamaat-ud-Dawam, a charity India and the international community say is a front for Lashkar, but has refused to take further action until it has proof of Pakistani involvement. Islamabad has not acknowledged that Kasab is Pakistani, saying it has had no confirmation of his citizenship.

Kasab is the only accused gunman to survive the three-day standoff with police that followed the attack on two luxury hotels, a train station, a Jewish center and other sites in India's bustling commercial capital.